6. The Panofsky Ratio
There are two main purposes in a measurement of the Panofsky Ratio (P).
An accurate value of P allows the determination of the detector
acceptance for photons in the energy regime of m p 0/2 and,
furthermore, P is directly related to the isovector pion-nucleon
scattering length b1 which is an important parameter for pion
photoproduction cross sections. To motivate a re-measurement of P, in
the first place the theory of p N scattering shall be introduced followed by
the experimental set-up and the kinematics. Finally, the analysis of the
Panofsky ratio measurement will be given in the subsequent chapter.